Preparation method of lithium fluorosulfonate solution, lithium fluorosulfonate solution and application of lithium fluorosulfonate solution

Abstract

The invention discloses a preparation method of a lithium fluorosulfonate solution, the lithium fluorosulfonate solution and application thereof, belongs to the technical field of additives of lithium ion battery electrolytes, and overcomes the defects that lithium chlorosulfonate and chloride ions exist in lithium fluorosulfonate prepared by an existing production process and the process is complex. The preparation method of the lithium fluorosulfonate solution comprises the step of reacting sulfur trioxide with lithium fluoride in a non-aqueous solvent to prepare the lithium fluorosulfonate solution. The lithium fluorosulfonate is obtained through the addition reaction of sulfur trioxide and lithium fluoride, the raw materials are simple, the product is single, chloride ions are not introduced, impurities difficult to separate are not generated, the purity of the lithium fluorosulfonate in the prepared lithium fluorosulfonate solution is high, and the preparation process is simple.

Description

Technical Field

[0001] The present invention belongs to the technical field of additives for lithium-ion battery electrolytes, and particularly relates to a preparation method of lithium fluorosulfonate solution, a lithium fluorosulfonate solution and its application. Background Art

[0002] Lithium fluorosulfonate is a new type of lithium salt and can be used as an additive for lithium-ion battery electrolytes. When lithium fluorosulfonate is used as an additive for lithium-ion batteries, the high-temperature charge and discharge cycle characteristics of lithium batteries can be greatly improved, and a high battery capacity retention rate can be maintained.

[0003] Currently, in the known manufacturing methods of lithium fluorosulfonate, most are reactions of fluorosulfonic acid with lithium salts. There are many side reactions and by-products in this reaction, bringing many impurities, affecting the yield. At the same time, fluorosulfonic acid used as a raw material easily reacts with moisture in the air to generate hydrogen fluoride, which is difficult to handle. This severely limits the production and use of lithium fluorosulfonate.

[0004] The prior art discloses a method for producing lithium fluorosulfonate by reacting chlorosulfonic acid with lithium fluoride in a non-aqueous solvent. However, the reaction of chlorosulfonic acid with lithium fluoride includes two-step reactions: First, the fluorination reaction of lithium fluoride with chlorosulfonic acid to generate fluorosulfonic acid and lithium chloride, and then the ion exchange of fluorosulfonic acid and lithium chloride to obtain lithium fluorosulfonate and hydrogen chloride. This process has the situation that chlorosulfonic acid is not completely fluorinated, there is some chlorosulfonic acid left, and chlorosulfonic acid undergoes ion exchange to generate lithium chlorosulfonate, and it is very difficult to separate lithium chlorosulfonate from lithium fluorosulfonate. At the same time, due to the use of chlorosulfonic acid, hydrogen chloride gas is generated in the reaction products. This gas has a large solubility in the solvent, and for lithium battery materials, the requirement for chloride ions is very high, generally not higher than 5 ppm. Post-treatment to remove chloride ions requires purification steps such as vacuum degassing and recovery of the solvent by distillation to remove the dissolved hydrogen chloride, and the process is complex. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects that lithium chlorosulfonate and chloride ions exist in the lithium fluorosulfonate prepared by the existing production process and the process is complex, so as to provide a preparation method of lithium fluorosulfonate solution, a lithium fluorosulfonate solution and its application.

[0006] For this purpose, the present invention provides the following technical solutions.

[0007] In the first aspect, the present invention provides a preparation method of lithium fluorosulfonate solution, including: reacting sulfur trioxide with lithium fluoride in a non-aqueous solvent to obtain a lithium fluorosulfonate solution.

[0008] In a possible implementation manner, the molar amount of the sulfur trioxide ≤ the molar amount of the lithium fluoride;

[0009] Preferably, the molar ratio of sulfur trioxide to lithium fluoride is 1.0:(1.02 - 1.10).

[0010] In a possible implementation, sulfur trioxide and lithium fluoride are reacted in a non-aqueous solvent, and then the insoluble substances are removed by filtration.

[0011] In a possible implementation, the reaction solution after removing the insoluble substances by filtration is deacidified.

[0012] Optionally, a deacidification resin is used for deacidification.

[0013] Optionally, the deacidification resin is an ion exchange resin. Optionally, the ion exchange resin includes one or more of weakly basic macroporous polystyrene resin and FB type weakly basic deacidification resin.

[0014] In a possible implementation, the temperature of the reaction is 0 - 100 °C, and the reaction time is 4 - 12 h.

[0015] Preferably, the temperature of the reaction is 40 - 60 °C.

[0016] In a possible implementation, the water content of the non-aqueous solvent is less than 10 ppm.

[0017] In a possible implementation, the non-aqueous solvent includes one or more of carbonates, carboxylates, ethers, nitriles, and amides.

[0018] Optionally, the carbonate includes at least one of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0019] Optionally, the carboxylate includes at least one of ethyl acetate, methyl acetate, and ethyl formate.

[0020] Optionally, the amide includes at least one of dimethylformamide and diethylformamide.

[0021] Optionally, the ether includes at least one of ethylene glycol dimethyl ether and tetrahydrofuran.

[0022] Optionally, the nitrile includes at least one of acetonitrile, isobutyronitrile, and propionitrile.

[0023] In a possible implementation, the process of preparing the lithium fluorosulfonate solution is carried out under a protective atmosphere.

[0024] Optionally, the protective atmosphere includes at least one of nitrogen, argon, and helium.

[0025] In a possible implementation, a PTFE (polytetrafluoroethylene) flat membrane is used for filtration.

[0026] Preferably, a modified PTFE flat membrane is used for filtration. The preparation method of the modified PTFE flat membrane includes: performing plasma pretreatment on the PTFE flat membrane in a nitrogen atmosphere, with the plasma pretreatment power being 70 - 500 W and the pretreatment time being 25 - 200 s. Subsequently, the pretreated PTFE flat membrane is washed with deionized water and dried to obtain a PTFE modified flat membrane.

[0027] In a possible implementation manner, the operating temperature for acid removal is 0 - 100 °C;

[0028] Optionally, the time for acid removal is 5 - 6 h.

[0029] In a second aspect, the present invention provides a lithium fluorosulfonate solution prepared by the above preparation method.

[0030] Optionally, the concentration of the lithium fluorosulfonate solution is 25% - 35%.

[0031] In a third aspect, the present invention provides the application of the lithium fluorosulfonate solution in a lithium-ion battery.

[0032] After reacting sulfur trioxide with lithium fluoride in a non-aqueous solvent, insoluble substances (the insoluble substances are lithium fluoride) are removed by filtration. The filtration is carried out using a precision filter, and the filter membrane in the precision filter uses a PTFE flat membrane.

[0033] The filtered reaction solution is subjected to refining processes such as resin acid removal to obtain a high-purity lithium fluorosulfonate solution. Acidic impurities such as hydrogen fluoride and sulfuric acid are removed through an ion exchange resin.

[0034] When the concentration of the lithium fluorosulfonate solution is 30 ± 5%, it can be directly used to prepare an electrolyte.

[0035] The technical solution of the present invention has the following advantages:

[0036] The preparation method of the lithium fluorosulfonate solution of the present invention includes: reacting sulfur trioxide with lithium fluoride in a non-aqueous solvent to prepare a lithium fluorosulfonate solution. In the prior art, chloride ions are introduced during the preparation of the lithium fluorosulfonate solution, and the chloride ions will react with the solvent or lithium salt in the electrolyte to generate harmful by-products, affecting the battery performance. In the present invention, sulfur trioxide and lithium fluoride undergo an addition reaction to obtain lithium fluorosulfonate. The raw materials are simple and the product is single. Chloride ions are not introduced, and impurities that are difficult to separate are not generated. The purity of lithium fluorosulfonate in the prepared lithium fluorosulfonate solution is relatively high. Moreover, sulfur trioxide belongs to bulk raw materials and is easy to obtain as a raw material. In addition, there are no other side reaction problems during the reaction, and the generated product is single. The purity and yield of the obtained product are very high. Also, the raw materials of the present invention do not require hydrogen fluoride, and the product does not generate hydrogen fluoride. The method of the present invention has low requirements for equipment and simple post-treatment of the product, and is suitable for large-scale industrial production in the preparation of electrolytes for lithium batteries.

[0037] The preparation method provided by the present invention has mild reaction conditions, high yield of the obtained product, and cheap and easily available reaction raw materials, which can greatly save costs. The lithium fluorosulfonate solution prepared by the present invention has a high purity of lithium fluorosulfonate and can ensure the working performance of the battery when used as a lithium battery additive. Detailed implementation manners

[0038] The present invention intends to cover all alternatives, modifications and equivalent technical solutions, which are all included within the scope of the present invention as defined in the claims. Those skilled in the art should recognize that many methods and materials similar or equivalent to those described herein can be used to practice the present invention. The present invention is in no way limited to the methods and materials described herein. In the case where one or more of the incorporated documents, patents and similar materials are different from or contradictory to the present application (including but not limited to the defined terms, term applications, described technologies, etc.), the present application shall prevail.

[0039] It should be further recognized that certain features of the present invention are described in multiple independent embodiments for clarity, but can also be provided in combination in a single embodiment. Conversely, various features of the present invention are described in a single embodiment for brevity, but can also be provided separately or in any suitable sub-combination.

[0040] Unless otherwise stated, all scientific and technical terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. All patents and published publications related to the present invention are incorporated herein by reference in their entirety.

[0041] Unless otherwise stated, the following definitions shall apply to the present invention. For the purposes of the present invention, chemical elements are consistent with the CAS version of the periodic table of elements and the 75th edition (1994) of the Handbook of Chemistry and Physics. The entire content thereof is incorporated into the present invention.

[0042] The term "comprising" or "including" is an open-ended expression, that is, it includes the content specified in the present invention, but does not exclude other aspects.

[0043] The present invention provides a method for preparing a lithium fluorosulfonate solution by reacting with cheap and easily available raw materials at a lower temperature and conditions. The method includes: under a protective atmosphere, reacting sulfur trioxide with lithium fluoride suspended in a non-aqueous solvent to obtain a reaction solution, and subjecting the reaction solution to precision filtration and resin deacidification and refining to obtain a high-quality lithium fluorosulfonate solution.

[0044] The reaction equation of this method is as follows:

[0045] SO 3 + LiF = LiSO 3 F

[0046] In some embodiments, the molar ratio of sulfur trioxide to lithium fluoride is 1:(1.02 to 1.10), for example: 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09, 1:1.10.

[0047] Preferably, the water content of the lithium fluoride does not exceed 50 ppm.

[0048] In some embodiments, the non-aqueous solvent includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl acetate, dimethylformamide, ethylene glycol dimethyl ether, acetonitrile, and tetrahydrofuran.

[0049] Preferably, the water content of the non-aqueous solvent is less than 10 ppm.

[0050] The reaction temperature is 0 to 100 °C, and the reaction time is 4 to 12 h. Exemplarily, the reaction temperature can be 0 °C, 10 °C, 20 °C, 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C or 100 °C, and the reaction time can be 6 h, 7 h, 8 h, 9 h, 10 h, 11 h or 12 h.

[0051] Preferably, the reaction temperature is 40 to 60 °C.

[0052] Preferably, the reaction time is 8 to 10 h.

[0053] In some embodiments, the operating temperature for resin deacidification is 0 to 100 °C, preferably 0 to 60 °C, and the deacidification time is 4 to 8 h.

[0054] Preferably, the deacidification temperature is 30 to 40 °C.

[0055] Preferably, the deacidification time is 1 to 6 h.

[0056] The entire process of the preparation method of the lithium fluorosulfonate solution is carried out under a protective atmosphere, and the protective atmosphere includes at least one of nitrogen, argon, and helium.

[0057] The content of sulfate ions in the lithium fluorosulfonate solution prepared by the present invention is below 5 ppm; the concentration of acid in the solution is tested by titration, and the acidity (calculated as HF) is below 100 ppm. Since the content of sulfates and free acids in the solution is small, the solution can be directly used as a lithium battery additive material.

[0058] The following embodiments are provided to better understand the present invention further. It is not limited to the described optimal embodiment, and does not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with those of other prior arts falls within the protection scope of the present invention.

[0059] For those embodiments where specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments whose manufacturers are not indicated, they are all conventional reagent products that can be obtained through commercial purchase.

[0060] The dimethyl carbonate in the embodiment is purchased from Shandong Dongyue Chemical Co., Ltd. with a water content of 2 ppm; the lithium fluoride is purchased from Ganfeng Lithium Co., Ltd. with a water content of 15 ppm. The water content is measured by the Karl Fischer micro - moisture analysis method.

[0061] Example 1

[0062] This embodiment provides a preparation method of a lithium fluorosulfonate solution, including the following steps:

[0063] In a 500 - ml three - necked flask, under nitrogen protection, 200 ml of dimethyl carbonate and 26.72 g (1.03 mol) of lithium fluoride are added. While stirring, the temperature is slowly raised, and 80.06 g (1 mol) of sulfur trioxide is slowly added dropwise at 40°C, and the addition is completed in about 2 hours. Under the same temperature condition, keep warm for another 6 hours to end. After the reaction is completed, the temperature is lowered to room temperature. The reaction solution is filtered through a precision filter, and the concentration is adjusted to about 31% by mass concentration of lithium fluorosulfonate with dimethyl carbonate. Then, it is subjected to deacidification treatment with a weakly basic macroporous polystyrene resin at room temperature for 4 hours. After precision filtration, a lithium fluorosulfonate solution with a weight concentration of 30% is obtained.

[0064] The filter membrane in the precision filter uses a PTFE - modified flat membrane. The preparation method of the PTFE - modified flat membrane includes: performing plasma pretreatment on the PTFE flat membrane in a nitrogen atmosphere, with a plasma pretreatment power of 120 W and a pretreatment time of 200 s. Subsequently, the pretreated PTFE flat membrane is washed with deionized water and dried to obtain the PTFE - modified flat membrane.

[0065] Detect the lithium fluorosulfonate solution prepared in Example 1:

[0066] Use nuclear magnetic resonance to detect the purity of lithium fluorosulfonate in the lithium fluorosulfonate solution.

[0067] Use the neutralization titration method to detect the content of free acid in the lithium fluorosulfonate solution.

[0068] Use the Karl Fischer method to detect the water content in the lithium fluorosulfonate solution.

[0069] The content of metal ions and sulfate ions in lithium fluorosulfonate solution was detected by ion chromatography.

[0070] Test results: The purity of lithium fluorosulfonate in the lithium fluorosulfonate solution was 99.92%, the content of free acid (calculated as HF) was 55 ppm, the water content was 123 ppm, the content of each alkali metal ion (calculated as K, Na) was below 2 ppm, the sulfate ion content was 6 ppm, and the heavy metal ion content (calculated as Fe) was 1 ppm.

[0071] Example 2

[0072] This example provides a preparation method of lithium fluorosulfonate solution, including the following steps:

[0073] In a three-necked flask, under nitrogen protection, 200 ml of dimethyl carbonate and 28.5 g (1.1 mol) of lithium fluoride were added. The temperature was slowly raised with stirring, and 80.06 g (1 mol) of sulfur trioxide was slowly added dropwise at 40 °C, and the addition was completed in about 2 hours. Under the same temperature condition, keep warm for another 5 hours to end. After the reaction, the temperature was lowered to room temperature. The reaction solution was filtered through a precision filter, and the concentration was adjusted to about 32% with dimethyl carbonate. Then, it was subjected to deacidification treatment with FB type weakly basic deacidification resin at room temperature. After precision filtration, a lithium fluorosulfonate solution with a weight concentration of 30% was obtained.

[0074] The filter membrane in the precision filter was a PTFE modified flat membrane. The preparation method of the PTFE modified flat membrane included: performing plasma pretreatment on the PTFE flat membrane in a nitrogen atmosphere, with a plasma pretreatment power of 350 W and a pretreatment time of 100 s. Subsequently, the pretreated PTFE flat membrane was washed with deionized water and dried to obtain the PTFE modified flat membrane.

[0075] Test results: The purity of lithium fluorosulfonate in the lithium fluorosulfonate solution was 99.91%, the free acid (calculated as HF) was 67 ppm, the water content (Karl Fischer method) was 83 ppm, the content of each alkali metal ion (calculated as K, Na) was below 1 ppm, the sulfate ion content was 8 ppm, and the heavy metal ion content (calculated as Fe) was 1 ppm.

[0076] Example 3

[0077] This example provides a preparation method of lithium fluorosulfonate solution, including the following steps:

[0078] In a 2000 ml three-necked flask, under nitrogen protection, 1000 ml of dimethyl carbonate and 131 g (5.05 mol) of lithium fluoride were added. The mixture was stirred and slowly heated, and 400.3 g (5 mol) of sulfur trioxide was slowly added dropwise at 50°C over about 3 hours. After the addition was completed, the temperature was maintained at the same level for 6 hours. After the reaction ended, the temperature was cooled to room temperature. The reaction solution was filtered precisely, the concentration was adjusted with dimethyl carbonate, and then it was subjected to deacidification treatment through a deacidification resin. After precise filtration, a lithium fluorosulfate solution with a weight concentration of 30% was obtained.

[0079] The filter membrane in the precision filter is a PTFE-modified flat membrane. The preparation method of the PTFE-modified flat membrane includes: performing plasma pretreatment on the PTFE flat membrane in a nitrogen atmosphere. The plasma pretreatment power is 500 W and the pretreatment time is 50 s. Subsequently, the pretreated PTFE flat membrane is washed with deionized water and dried to obtain the PTFE-modified flat membrane.

[0080] Test results: The purity of lithium fluorosulfate in the lithium fluorosulfate solution is 99.92%, the free acid (calculated as HF) is 84 ppm, the moisture (Karl Fischer method) is 35 ppm, the content of each alkali metal ion (calculated as K, Na) is below 1 ppm, the content of sulfate ion is 7 ppm, and the content of heavy metal ions (calculated as Fe) is 1 ppm.

[0081] Example 4

[0082] This example provides a preparation method of a lithium fluorosulfate solution, including the following steps:

[0083] In a 500 ml three-necked flask, under nitrogen protection, 200 ml of ethyl methyl carbonate and 26.72 g (1.03 mol) of lithium fluoride were added. The mixture was stirred and slowly heated, and 80.06 g (1 mol) of sulfur trioxide was slowly added dropwise at 50°C over about 2 hours. After the addition was completed, the temperature was maintained at the same level for 8 hours. After the reaction ended, the temperature was cooled to room temperature. The reaction solution was filtered through a precision filter, the concentration was adjusted with ethyl methyl carbonate, and then it was soaked in a FB type weakly basic macroporous deacidification resin at room temperature for 4 hours for deacidification treatment. After precise filtration, a lithium fluorosulfate solution with a weight concentration of 30% was obtained.

[0084] The filter membrane in the precision filter is a PTFE-modified flat membrane. The preparation method of the PTFE-modified flat membrane includes: performing plasma pretreatment on the PTFE flat membrane in a nitrogen atmosphere. The plasma pretreatment power is 120 W and the pretreatment time is 200 s. Subsequently, the pretreated PTFE flat membrane is washed with deionized water and dried to obtain the PTFE-modified flat membrane.

[0085] Test results: The purity of lithium fluorosulfonate in the lithium fluorosulfonate solution is 99.45%, the free acid (calculated as HF) is 86 ppm, the water content (Karl Fischer method) is 94 ppm, the content of each alkali metal ion (calculated as K, Na) is less than 1 ppm, the sulfate ion content is 15 ppm, and the heavy metal ion content (calculated as Fe) is 1 ppm.

[0086] Example 5

[0087] This example provides a preparation method of a lithium fluorosulfonate solution, including the following steps:

[0088] In a 500 ml three-necked flask, under nitrogen protection, add 200 ml of dimethyl carbonate and 25.94 g (1 mol) of lithium fluoride. Stir and slowly heat up, and slowly dropwise add 80.06 g (1 mol) of sulfur trioxide at 60 °C. The addition is completed in about 2 hours. Maintain the same temperature condition and continue to keep warm for 6 hours to end. After the reaction ends, maintain the same temperature condition. After the reaction ends, cool down to room temperature. After the reaction solution is filtered precisely, adjust the concentration with dimethyl carbonate, then carry out deacidification treatment through a deacidification resin, and after precise filtration, obtain a lithium fluorosulfonate solution with a weight concentration of 30%.

[0089] The filter membrane in the precision filter uses the unmodified PTFE flat membrane in Example 1.

[0090] Test results: The purity of lithium fluorosulfonate in the lithium fluorosulfonate solution is 98.66%, the free acid (calculated as HF) is 257 ppm, the water content (Karl Fischer method) is 32 ppm, the content of each alkali metal ion (calculated as K, Na) is below 1 ppm, the sulfate ion content is 66 ppm, and the heavy metal ion content (calculated as Fe) is 2 ppm.

[0091] Example 6

[0092] This comparative example provides a preparation method of a lithium fluorosulfonate solution, including the following steps:

[0093] In a 500 ml three-necked flask, under nitrogen protection, add 200 ml of dimethyl carbonate and 25.94 g (1 mol) of lithium fluoride. Stir and slowly heat up, and slowly dropwise add 80.06 g (1 mol) of sulfur trioxide at 50 °C. The addition is completed in about 2 hours. Maintain the same temperature condition and continue to keep warm for 6 hours to end. After the reaction ends, cool down to room temperature. After the reaction solution is filtered precisely, adjust the concentration with dimethyl carbonate, then carry out deacidification treatment through a deacidification resin, and after precise filtration, obtain a lithium fluorosulfonate solution with a weight concentration of 30%.

[0094] The filter membrane in the precision filter adopts a PTFE modified flat membrane. The preparation method of the PTFE modified flat membrane includes: performing plasma pretreatment on the PTFE flat membrane in a nitrogen atmosphere, with a plasma pretreatment power of 120 W and a pretreatment time of 200 s. Subsequently, the pretreated PTFE flat membrane is washed with deionized water and dried to obtain the PTFE modified flat membrane.

[0095] Test results: The purity of lithium fluorosulfonate in the lithium fluorosulfonate solution is 98.36%, the free acid (calculated as HF) is 168 ppm, the moisture (Karl Fischer method) is 186 ppm, the content of each alkali metal ion (calculated as K, Na) is below 3 ppm, the content of sulfate ion is 16 ppm, and the content of heavy metal ions (calculated as Fe) is 1 ppm.

[0096] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing a lithium fluorosulfonate solution, characterized in that: include: The sulfur trioxide and lithium fluoride are reacted in a non-aqueous solvent to prepare a lithium fluorosulfonate solution.

2. The method for preparing the lithium fluorosulfonate solution according to claim 1, characterized in that: The molar amount of sulfur trioxide is less than or equal to the molar amount of lithium fluoride; Preferably, the molar ratio of sulfur trioxide to lithium fluoride is 1.0:(1.0-1.10), more preferably 1.0:(1.02-1.10).

3. The method for preparing the lithium fluorosulfonate solution according to claim 2, characterized in that: After sulfur trioxide and lithium fluoride are reacted in a non-aqueous solvent, insoluble matter is removed by filtration.

4. The method for preparing the lithium fluorosulfonate solution according to claim 3, characterized in that: Deacidifying the reaction solution after filtering to remove insoluble matter; Optionally, deacidification is performed using a deacidification resin; Optionally, the deacidification resin is an ion exchange resin. Optionally, the ion exchange resin includes one or more of a weakly alkaline macroporous polystyrene resin and a FB-type weakly alkaline deacidification resin.

5. The method for preparing the lithium fluorosulfonate solution according to any one of claims 1 to 4, characterized in that: The reaction temperature is 0 to 100°C and the reaction time is 4 to 12 hours; Preferably, the reaction temperature is 40-60°C.

6. The method for preparing the lithium fluorosulfonate solution according to any one of claims 1 to 4, characterized in that: At least one of the following conditions is met: (1) The water content of the non-aqueous solvent is less than 10 ppm; (2) the non-aqueous solvent comprises one or more of carbonates, carboxylates, ethers, nitriles, and amides; Optionally, the carbonate includes at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; Optionally, the carboxylic acid ester includes at least one of ethyl acetate, methyl acetate, and ethyl formate; Optionally, the amides include at least one of dimethylformamide and diethylformamide; Optionally, the ethers include at least one of ethylene glycol dimethyl ether and tetrahydrofuran; Optionally, the nitrile includes at least one of acetonitrile, isobutyronitrile and propionitrile; (3) The process of preparing the lithium fluorosulfonate solution is carried out under a protective atmosphere; Optionally, the protective atmosphere includes at least one of nitrogen, argon and helium.

7. The method for preparing the lithium fluorosulfonate solution according to claim 3, characterized in that: Filtration was performed using a PTFE flat membrane; Preferably, a modified PTFE flat membrane is used for filtration, and the preparation method of the modified PTFE flat membrane includes: subjecting the PTFE flat membrane to plasma pretreatment in a nitrogen atmosphere, the plasma pretreatment power is 70 to 500 W, and the pretreatment time is 25 to 200 s, and then the pretreated PTFE flat membrane is washed with deionized water and dried to obtain a PTFE modified flat membrane.

8. The method for preparing the lithium fluorosulfonate solution according to claim 4, characterized in that: The deacidification operating temperature is 0 to 100°C; Optionally, the deacidification time is 1 to 6 hours.

9. A lithium fluorosulfonate solution prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the lithium fluorosulfonate solution according to claim 9 in lithium ion batteries.